Master cylinders of this type are very widely used nowadays.
A problem which commonly arises in tandem master cylinders is of contriving for the pressure in the secondary chamber to be as close as possible to that prevailing in the primary chamber.
One of the difficulties to be overcome in order to solve this problem lies in the conflicting nature of two requirements, namely on the one hand the need to reduce friction between the cylinder and the various seals, especially the second one, in order to reduce the pressure difference between the chambers and, on the other hand, the need to ensure that the seals are leaktight even for the highest pressures that the master cylinder is to be capable of delivering.